1. Field of the Invention
The invention relates to a hydraulic actuating system for movable parts, particularly for hinged movable covers on vehicles with at least one working cylinder that has a piston with sealing means fitted against a cylinder wall whereby a control unit is connected to one or all cylinders and with a pressure sensor in a common hydraulic circuit. The invention relates further to a vehicle convertible top and a method to adjust its position and/or identify a working cylinder in a hydraulic actuating system whereby the pressure in the hydraulic circuit is monitored by a pressure sensor and where a corresponding signal is received and analyzed by a control unit.
2. The Prior Art
A hydraulic actuating system for a vehicle top is known from patent AT-PS 402 280, whereby a pressure sensor is placed in the common hydraulic circuit of the working cylinder and whereby the pressure sensor is connected to a control unit for separate switching elements of the cylinder. The outgoing signal of the pressure sensor is used to control the end-of-stroke position of each cylinder taking into account the progression of the pressure values and a predetermined switching sequence of the individual switching elements. Without costly separate end-position switches at each cylinder or the corresponding part of a convertible top system, the control system for the entire system can be simplified; but the cylinders may only be controlled in a predetermined switching sequence and changes in the switching sequence would necessitate a new setup for the entire control program. Above all, there is no possibility of recognizing intermediate positions of the working cylinder and to allow, for example, overlapping movements of the cylinders or with external operations.
It is therefore the object of the invention to produce a hydraulic actuating system for general utilization purposes, which avoids the above-mentioned disadvantages with maximum simplicity and which makes possible in regard to production, assembly and maintenance, a cost-effective construction, a flexible programmable control system as well as a time-saving overlapping or parallel operating work cycle of the cylinder in the hydraulic actuating system. Additional objects of the invention are a vehicle convertible top system, which would also have the above mentioned characteristics and would provide a simple, inexpensive and reliable method for controlling positions and/or identification of a working cylinder in a hydraulic actuating system.